Method for production of a coated substrate with controlled surface characteristics

Abstract

A crystalline, porous, synthetic material is disclosed, together with its related preparation process. Such a material of zeolitic character, containing silicon, titanium and iron oxides, corresponds, in its calcined and anhydrous state, to the following empi rical formula pHFeO.sub.2.qTiO.sub.2.SiO.sub.2 wherein p has a value greater than zero and lower than or equal to 0.050, q has a value greater than zero and lower than or equal to 0.025, and the H + of HFeO 2 can be at least partly replaceable or replaced by cations.

We claim: 
     
       1. Process for preparing a synthetic crystalline and porous material having a zeolite nature, containing oxides of silicon, titanium and iron, having, in its calcined and anhydrous state the empirical formula:   pHFeO.sub.2.qTiO.sub.2.SiO.sub.2     wherein p has a value greater than zero and smaller than or equal to 0.050, and q has a value greater than zero and smaller than or equal to 0.025, the hydrogen of HFeO 2  being at least partially substitutable by cations, said process comprising: reacting under hydrothermal conditions a source of silicon, a source of titanium, a source of iron and a nitrogenous organic base, with a SiO 2  /Fe 2  O 3  molar ratio in the reaction mixture greater than 50, with a SiO 2  /TiO 2  molar ratio in the reaction mixture greater than 5, and with a H 2  O/SiO 2  molar ratio from 10 to 100, at a temperature from 120° C. to 200° C., at a pH from 9 to 14 and for a time from 1 hour to 5 days.   
     
     
       2. The process according to claim 1, wherein in the reaction mixture the SiO 2  /Fe 2  O 3  molar ratio is between 150 and 600, the SiO 2  /TiO 2  molar ratio is between 15 and 25, and the H 2  O/SiO 2  molar ratio is between 30 and 50. 
     
     
       3. The process according to claim 1, wherein said silicon source is selected from the group consisting of silica gel, silica sol and alkyl silicates, said titanium source is selected from salts and organic sources of titanium, said iron source is selected from the group consisting of salts, hydroxides and organic sources of iron. 
     
     
       4. The process according to claim 3, wherein said alkyl silicates are tetraethyl silicate. 
     
     
       5. The process according to claim 3, wherein said titanium salts are halides. 
     
     
       6. The process according to claim 3, wherein said organic sources of titanium are alkyl titanates. 
     
     
       7. The process according to claim 6, wherein said alkyl titanates are tetraethyltitanate. 
     
     
       8. The process according to claim 3, wherein said iron salts are selected from the group consisting of halides and nitrates. 
     
     
       9. The process according to claim 3, wherein said organic sources of iron are alkoxides. 
     
     
       10. The process according to claim 1, wherein said organic base is alkylammonium hydroxide. 
     
     
       11. The process according to claim 10, wherein said alkylammonium hydroxide is tetrapropylammonium hydroxide. 
     
     
       12. The process according to claim 1, wherein said process occurs at a temperature from 160° C. to 180° C., at a pH from 10 to 12 and for a time ranging from 3 hours to 10 hours. 
     
     
       13. The process according to claim 11, wherein in the reaction mixture a TPA +  /SiO 2  molar ratio is from 0.1 to 1. 
     
     
       14. The process according to claim 13, wherein in the reaction mixture said TPA +  /SiO 2  molar ratio is from 0.2 to 0.4. 
     
     
       15. The process according to claim 1 wherein the reaction is conducted in the presence of one or more salts and/or hydroxides of alkali metals or alkaline earth metals, with a M +  /SiO 2  molar ratio in the reaction mixture, wherein M +  is an alkali-metal or an alkaline earth metal cation, smaller than 0.10. 
     
     
       16. The process according to claim 1 wherein in the reaction there is a SiO 2  /Fe 2  O 3  molar ratio in the crystalline material higher than about 250 and a SiO 2  /TiO 2  molar ratio in the crystalline material of about 44 is produced. 
     
     
       17. The process according to claim 16 wherein in the reaction mixture there is a SiO 2  /Fe 2  O 3  molar ratio in the crystalline material higher than about 250 and a SiO 2  /TiO 2  molar ratio in the crystalline material of about 44 is produced.